[Study on Some Factors Affecting of Urea Concentration in Milk of Cows and its Relationship to Milk Yield and Composition]

This study was conducted on 39 dairy cows of the Holstein Friesian race at two farms, a governmental college Farm (Charabo) and a private farm in the province of Damascus, in order to determine the level of concentration of urea and other milk constituents. Animals were divided into three groups according to the stage of lactation, up to 100 days and from 101 to 200 days and more than 200 days. Each group included a total of 13 cows, 7 cows on a college farm and 6 cows on the private farm. Submitted to the cattle study its nutritional requirements from the preservatives and productivity, according to the nutrition program used in each farm and the same regime of feeding, as it was feeding on the governmental farm automatic for the concentrated fodder, and the rough fodder introduced a semi-automatic and separate from the concentrate, while in the private farm introduced feed by hand after mixing the concentrate feed with the rough feed. The level of concentration of urea and other milk constituents was estimated in the two dairy farms and in the morning and evening milking and in the stage of lactation. Data were analyzed in statistical program SAS using variance analysis ANOVA of repeated measurements, and to detect the significant differences between the averages was used Bonferroni Test. The results of statistical analysis indicated a significant differences in the percentage of fat (3.60 compared to 3.88%), protein (3.52 compared 3.59%), lactose (4.77 compared 4.88%), solids-non-fat (SNF) (9.04 compared 9.22%), dry matter (12.63 compared to 13.10%) and urea (231 compared to 335 mg / liter), while not observed significant differences in the amount of daily milk yield (22.41 compared to 20.86 kg), density (1.0319 compared to 1.0321) and pH (6.73 compared 6.73) in the two farms of public and private, respectively. Did not notice the presence of significant differences in urea concentration and the percentage of protein, lactose, SNF and the degree of acidity in milk during morning and evening milking, while the significant effect was observed clearly for the rest of other milk constituents. Did not see the significant influence of the stage of lactation on the level of urea, the percentage of lactose and the degree of acidity in milk, while its effect was clear in the rest of other milk constituents